1. Field of the Invention
The present invention relates generally to a shifter for the actuation of transmissions on bicycles, in particular a twist-grip shifter which is suitable for installation on tube ends. The shifter primarily includes a stationary housing connected to the tube end and a housing, which housing has at least one lever, can be rotated by hand and is fixed in position axially in relation to the stationary housing. The stationary housing and the rotational housing form a single unit. Furthermore, the stationary housing has a projection or shoulder, which projection has a cable guide in a slot to guide a traction cable, and an abutment to support a shell, covering, wrapper or sheath around the traction cable. There can also be an opening for the insertion of the traction cable.
2. Background Information
German Utility Model G 94 12 207.5 describes a modified twist-grip shifter in a housing. The housing has a hole, through which hole the shifter cable can be replaced without having to disassemble the shifter grip. The hole in question has a diameter which is sufficient for the introduction of the shifter cable, but not its nipple, which nipple is fixed in the rotational housing of the modified twist-grip shifter. The shifter cable can therefore, only be replaced if the cable can be extracted from the overall system in the direction of the nipple. Consequently, the bicycle transmission must be detached from the shifter cable and thus from the shifter. The present invention, however, teaches that the traction cable and its shell can be connected to the shifter without having to detach the traction cable from the bicycle transmission. All that is necessary is to relax the shifter cable with respect to the shell by a traction cable adjustment and/or by shifting the transmission to a specified speed, so that a sufficient length of cable remains to suspend the nipple in the twist-grip shifter without having to release the shifter cable from the transmission.
Registration No. M 90 06 158.6 in the register of designs of the Federal Republic of Germany, also describes a twist-shifter for bicycle handlebars. The rotational housing of the twist-shifter has a fixing device for the nipple of the traction cable, whereby the traction cable can also be extracted from the shifter toward the nipple and re-introduced. The rotational housing also has actuator lugs in the radial direction which make possible an ergonomically efficient actuation of the bicycle transmission because their shape is adapted to the shape of the rider's hand. Here again, however, the disadvantage is that when the shifter cable is uncoupled from the twist-grip shifter, the cable must also be disconnected from the bicycle transmission, to replace either the shifter cable or the twist-grip shifter.
German Patent 936 666 describes a twist-grip for controlling the carburetor on motorcycles. An advantage of the twist-grip is that it employs simple means to simplify the suspension and removal of the cable nipple in comparison to similar known devices. The nipple of the actuator cable is installed and suspended by means of a spring-mounted or flexible suspension mechanism, which suspension mechanism projects out of a closable opening in one extreme position of the twist-grip. After the introduction of the cable shell into its specified position, the opening can be closed and the traction cable is then functional without having to disconnect the traction cable from the carburetor to which it is connected. The functionally correct principle taught by this patent is applicable to twist-grip shifters for bicycles only to a limited extent, however, because the space available in indexed twist-grip shifters does not permit the installation of such a structure, and on the other hand, for reasons of efficiency and economy, no additional costs for the cable suspension should be incurred.